In patients with inflammatory bowel disease serum antibody is produced to intestinal antigens and lymphocytes reactive to intestinal epithelial cells are also formed. It is not known what role these immune components have in the pathogenesis of the tissue lesions in patients with inflammatory bowel disease. In an experimental system we have been able to produce histologic changes in the colon suggestive of those seen in inflammatory bowel disease. This has been done by active immunization of both rabbits and guinea pigs, adoptive transfer of lymphocytes from immunized guinea pigs to normal syngeneic animals and by the production of a non-specific cell mediated immune response within the colon. These procedures will be extended to determine if the tissue changes are indeed due to a cell mediated immune mechanism and if so what effect serum antibody has on blocking the cytotoxic potential of lymphocytes. In addition, the effect on the disease process of altering the T lymphocyte population will be evaluated. A hypothetical model of the disease will be established by following the immune response to the colon of animals undergoing a non-specific cell mediated immune response in the colon. The capability of the resultant colon sensitized lymphocytes to mediate colonic disease in normal animals will be determined.